Slurry distribution device for chemical mechanical polishing

ABSTRACT

An apparatus for chemical mechanical polishing includes a rotatable platen having a surface to support a polishing pad, a carrier head to hold a substrate in contact with the polishing pad, and a polishing liquid distribution system. The polishing liquid distribution system includes a dispenser positioned to deliver a polishing liquid to a portion of a polishing surface of the polishing pad, and a first barrier positioned before the portion of the polishing surface and configured to block used polishing liquid from reaching the portion of the polishing surface. The first barrier includes a solid first body having a first flat bottom surface and having a first leading surface configured to contact the used polishing liquid.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser.No. 62/354,563, filed on Jun. 24, 2016, and claims priority to U.S.Provisional Application Ser. No. 62/510,532, filed on May 24, 2017, thedisclosures of which are incorporated by reference.

TECHNICAL FIELD

The present disclosure relates to distribution of a polishing liquid,e.g., an abrasive slurry, during chemical mechanical polishing of asubstrate.

BACKGROUND

An integrated circuit is typically formed on a substrate by thesequential deposition of conductive, semiconductive, or insulativelayers on a silicon wafer. A variety of fabrication processes requireplanarization of a layer on the substrate. For example, one fabricationstep involves depositing a conductive filler layer on a patternedinsulative layer to fill the trenches or holes in the insulative layer.The filler layer is then polished until the raised pattern of theinsulative layer is exposed. After planarization, the portions of theconductive filler layer remaining between the raised pattern of theinsulative layer form vias, plugs and lines that provide conductivepaths between thin film circuits on the substrate. Planarization canalso be used to smooth and remove, to a desired thickness, an insulativelater that overlies a patterned conductive layer.

Chemical mechanical polishing (CMP) is one accepted method ofplanarization. This planarization method typically requires that thesubstrate be mounted on a carrier head. The exposed surface of thesubstrate is placed against a rotating polishing pad. The carrier headprovides a controllable load on the substrate to push it against thepolishing pad. A polishing liquid, such as slurry with abrasiveparticles, is supplied to the surface of the polishing pad.

SUMMARY

In one aspect, an apparatus for chemical mechanical polishing includes arotatable platen having a surface to support a polishing pad, a carrierhead to hold a substrate in contact with the polishing pad, and apolishing liquid distribution system. The polishing liquid distributionsystem includes a dispenser positioned to deliver a polishing liquid toa portion of a polishing surface of the polishing pad, and a firstbarrier positioned before the portion of the polishing surface andconfigured to block used polishing liquid from reaching the portion ofthe polishing surface.

Implementations of may include one or more of the following features.

The first barrier may be configured to contact the polishing surface inoperation. A first actuator may be configured to adjust a height of thefirst barrier relative to and/or a pressure of the first barrier on thepolishing surface. The first barrier may include a first wiper blade. Aleading edge of the first wiper blade may be oriented at an acute anglerelative to the polishing surface. The first wiper blade may include afirst portion having the acute angle and a second portion orientedparallel to the polishing surface. The dispenser may be positioned todeliver the polishing liquid onto a trailing surface of the first wiperblade. The dispenser may be positioned to deliver the polishing liquidto a section of the trailing surface on a side of the first wiper bladethat is closer to a center of the platen.

A second barrier may be positioned after the dispenser and may beconfigured to spread fresh polishing liquid delivered by the dispenserto the portion of the polishing surface. The second barrier may beconfigured to contact the polishing surface in operation. A secondactuator may be configured to adjust a height of the second barrierrelative to and/or a pressure of the second barrier on the polishingsurface. The second barrier may include a second wiper blade. A leadingedge of the second wiper blade may be oriented at an acute anglerelative to the polishing surface. The first barrier may be positionedparallel to the second barrier. The first barrier may extend to an edgeof the platen and the second barrier may be spaced from the edge of theplaten. The second barrier may be positioned higher than or press withlower pressure on the polishing pad than the first barrier.

An actuator may be configured to sweep the first barrier and/or thesecond barrier laterally across the polishing pad. A reservoir may holdthe polishing liquid, the dispenser may be fluidically coupled to thereservoir, and the polishing liquid may be an abrasive slurry.

In another aspect, an apparatus for chemical mechanical polishingincludes a rotatable platen having a surface to support a polishing pad,a carrier head to hold a substrate in contact with the polishing pad,and a polishing liquid distribution system. The polishing liquiddistribution system includes a dispenser positioned to deliver apolishing liquid to a portion of a polishing surface of the polishingpad, and a first barrier positioned before the portion of the polishingsurface and configured to block used polishing liquid from reaching theportion of the polishing surface. A leading surface of the first barriercurves between an inner end of the first barrier closer to a center ofthe platen and an outer end of the first barrier closer to an edge ofthe platen.

Implementations may include one or more of the following features.

The platen may be configured to rotate to provide a direction of motionbelow the first barrier, and the leading surface of the first barriermay be curved such that such that a concave side of the leading surfaceof the first barrier faces in the direction of motion.

A second barrier may be positioned after the dispenser and may beconfigured to spread fresh polishing liquid delivered by the dispenserto the portion of the polishing surface. A leading surface of the secondbarrier may be curved between an inner end of the second barrier closerto a center of the platen and an outer end of the second barrier closerto an edge of the platen. The leading surface of the second barrier maybe curved such that such that a concave side of the leading surface ofthe second barrier faces in the direction of motion. A radius ofcurvature of the second barrier may be less than a radius of curvatureof the first barrier.

In another aspect, an apparatus for chemical mechanical polishingincludes a rotatable platen having a surface to support a polishing pad,a carrier head to hold a substrate in contact with the polishing pad,and a polishing liquid distribution system. The polishing liquiddistribution system includes a dispenser positioned to deliver apolishing liquid to a portion of a polishing surface of the polishingpad, and a first barrier positioned before the portion of the polishingsurface and configured to block used polishing liquid from reaching theportion of the polishing surface. The first barrier includes a solidfirst body having a first flat bottom surface and having a first leadingsurface configured to contact the used polishing liquid.

Implementations may include one or more of the following features.

The body may have a width along a direction of motion of the polishingpad below the first barrier greater than a height of the first bodyperpendicular to the polishing surface.

A splash guard may project from the first leading surface. The firstleading surface of the first body of the first barrier may besubstantially vertical and the splash guard may project substantiallyhorizontally.

A second barrier may be positioned after the dispenser and may beconfigured to spread fresh polishing liquid delivered by the dispenserto the portion of the polishing surface. The second barrier may includea solid second body having a second flat bottom surface and having asecond leading surface configured to contact the fresh polishing liquid.The second leading surface may be oriented at an acute angle relative tothe polishing surface. The leading surface of the first body of thefirst barrier may be substantially vertical. The first barrier mayextend to an edge of the platen and the second barrier may be spacedfrom the edge of the platen. The second barrier may be positioned higherthan or press with lower pressure on the polishing pad than the firstbarrier.

In another aspect, an apparatus for chemical mechanical polishingincludes a rotatable platen having a surface to support a polishing pad,a carrier head to hold a substrate in contact with the polishing pad,and a polishing liquid distribution system. The polishing liquiddistribution system includes a dispenser positioned to deliver apolishing liquid to a portion of a polishing surface of the polishingpad, a first barrier positioned before the portion of the polishingsurface and configured to block used polishing liquid from reaching theportion of the polishing surface, a second barrier positioned after thedispenser and configured to spread fresh polishing liquid delivered bythe dispenser to the portion of the polishing surface, and a commonactuator coupled to the first barrier and the second barrier to adjust alateral position of the first barrier and the second barrier on thepolishing surface.

Implementations may include one or more of the following features.

The common lateral actuator may include an arm having a first endcoupled to the first barrier and the second barrier and a second endcoupled to a rotary actuator to sweep the arm laterally over the platen.A first actuator may be coupled between the first barrier and the armand a second actuator may be coupled between the second barrier and thearm. The first actuator may be configured to adjust a height of thefirst barrier relative to the polishing surface and/or a pressure of thefirst barrier on the polishing surface, and the second actuator may beconfigured to independently adjust a height of the second barrierrelative to the polishing surface and/or a pressure of the secondbarrier on the polishing surface.

Certain implementations can include one or more of the followingadvantages. Polishing uniformity can be improved. Defectivity can bereduced. Polishing can be less sensitive to pattern density, and dishingand erosion can be reduced. Slurry usage can be decreased, thus reducingcost of ownership. Polishing rates can be improved, or polishingpressure can be reduced while maintaining the polishing rate.

The details of one or more implementations are set forth in theaccompanying drawings and the description below. Other aspects, featuresand advantages will be apparent from the description and drawings, andfrom the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic side view, partially cross-sectional, of achemical mechanical polishing station that includes a slurrydistribution system.

FIG. 2A is a schematic top view of the chemical mechanical polishingstation of FIG. 1.

FIG. 2B is a schematic top view of another implementation of a chemicalmechanical polishing station.

FIG. 3 is a schematic side view, partially cross-sectional, of a slurrydistribution system.

FIG. 4 is a schematic top view of a portion of a chemical mechanicalpolishing station.

FIG. 5 is a schematic cross-sectional side view of an implementation ofa slurry distribution system with actuators.

FIG. 6 is a schematic cross-sectional side view of anotherimplementation of a slurry distribution system with actuators.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

One problem in chemical mechanical problem is sensitivity to patterndensity, e.g., as exhibited by erosion and dishing. By positioning abarrier to block used slurry from passing back beneath the substrate,the polishing process can be less sensitive to pattern density, anddishing and erosion can be reduced.

Another problem in chemical mechanical polishing is defectivity. Apotential contributor to defectivity is polishing by-products. A devicethat blocks used polishing liquid from returning to the region below thecarrier head can help reduce the polishing by-products from reaching thesubstrate during polishing.

Another problem in chemical mechanical polishing is within-wafernon-uniformity (WIWNU). A potential contributor to polishingnon-uniformity is non-uniform distribution of slurry to the interfacebetween the substrate and the polishing pad. By placing a slurryspreader in contact with the polishing pad, slurry can be spread acrossthe polishing pad in a more uniform manner.

FIG. 1 illustrates an example of a polishing station 20 of a chemicalmechanical polishing apparatus. The polishing station 20 includes arotatable disk-shaped platen 24 on which a polishing pad 30 is situated.The platen 24 is operable to rotate about an axis 25. For example, amotor 22 can turn a drive shaft 28 to rotate the platen 24.

The polishing pad 30 can be a two-layer polishing pad with a polishinglayer 32 and a softer backing layer 34. A plurality of grooves 38 can beformed in the polishing surface 36 of the polishing pad 30 (see FIG. 3).

The polishing station 22 can include a pad conditioner apparatus 40 witha conditioning disk 42 to maintain the condition of the polishing pad 30(see FIG. 2). The conditioning disk 42 may be positioned at the end ofan arm 44 that can move the disk 42 radially across the polishing pad30.

The carrier head 70 is operable to hold a substrate 10 against thepolishing pad 30. The carrier head 70 is suspended from a supportstructure 72, e.g., a carousel or a track, and is connected by a driveshaft 74 to a carrier head rotation motor 76 so that the carrier headcan rotate about an axis 71. Optionally, the carrier head 70 canoscillate laterally, e.g., on sliders on the carousel or track 72; or byrotational oscillation of the carousel itself. In operation, the platenis rotated about its central axis 25, and the carrier head is rotatedabout its central axis 71 and translated laterally across the topsurface of the polishing pad 30. Where there are multiple carrier heads,each carrier head 70 can have independent control of its polishingparameters, for example each carrier head can independently control thepressure applied to each respective substrate.

The carrier head 70 can include a flexible membrane 80 having asubstrate mounting surface to contact the back side of the substrate 10,and a plurality of pressurizable chambers 82 to apply differentpressures to different zones, e.g., different radial zones, on thesubstrate 10. The carrier head can also include a retaining ring 84 tohold the substrate.

A polishing liquid distribution system 100 delivers and spreads apolishing liquid, e.g., an abrasive slurry, on the surface of thepolishing pad 30. The polishing liquid distribution system 100 can alsoprevent used polishing liquid from returning to the substrate 10.

Referring to FIGS. 1 and 2A, the polishing liquid distribution system100 includes a dispenser 110 to deliver the polishing liquid 105 from areservoir 112 to the polishing pad 30. The dispenser 110 includes one ormore passages 114 having one or more ports 116 positioned over thepolishing pad 30. For example, the dispenser 110 can include a rigidbody through which the passage 114 extends, or the dispenser 110 caninclude flexible tubing supported by an arm. In either case, one or moreholes or nozzles coupled to the passage 114 can provide the ports 116.

The polishing liquid distribution system 100 also includes a firstbarrier 120 to block polishing liquid that has already passed under thecarrier head 70 or the conditioner disk 42 from reaching the location onthe polishing pad 30 where the dispenser 110 delivers the freshpolishing liquid. The first barrier 120 is positioned “before”—relativeto the direction of motion of the pad—the location on the polishing padwhere the dispenser 110 delivers the polishing liquid 105. For example,as shown in FIG. 2, if the platen 24 rotates counter-clockwise as shownby arrow A, then the first barrier 120 is positioned clockwise of thedispenser 110.

In some implementations, the first barrier 120 is positioned between thedispenser 110 and the conditioner 40 (or between the dispenser 110 andthe carrier head 70 if there is no conditioner). In someimplementations, the first barrier is positioned between the conditioner40 and the carrier head 70.

In some implementations, the first barrier 120 is a body that contactsthe surface 36 of the polishing pad 30 and generally blocks thepolishing liquid from passing underneath, except for any used polishingliquid that may be present in the grooves 38 and/or a thin film of usedpolishing liquid 105. The body of the first barrier can simply rest onthe polishing pad 30, or be positively pressed onto the polishing pad30, e.g., by an actuator. In some implementations, the first barrier 120is a body that sits slightly above the surface 36 of the polishing pad30.

The first barrier 120 can be generally elongated body, e.g., a linearbody (as shown in FIG. 2A), and can be oriented substantiallyperpendicular to the direction of motion of the platen 24, e.g.,generally along a radius of the platen 24. Alternatively, the firstbarrier can be canted at substantial angle relative to the radius of theplaten, e.g., 10-30°.

In some implementations, the first barrier 120 is a curved body, e.g.,as shown in FIG. 2B. The barrier 120 can curve such that the end closerto the outer edge of the platen 24 is further along the direction ofmotion (shown by arrow A) than the end that is closer to the center ofthe platen. The first barrier 130 can curve such that the concave sidefaces in the direction of motion.

A leading surface of the first barrier 120 be oriented at an angle of 15to 90 relative to the polishing surface 36 (see angle B in FIG. 3). Insome implementations, the leading surface is slanted relative to thepolishing surface, e.g., at an angle less than 90 degrees. In someimplementations, the leading surface is oriented vertically, i.e., at aright angle relative to the polishing surface. The leading surface ofthe first barrier 120 can slope, from top to bottom, in the direction ofmotion of the polishing pad (see arrow Ain FIG. 3).

In some implementations, the first barrier 120 is a wiper blade. Thefront surface of the wiper blade provides the leading surface of thefirst barrier 120. The wiper blade of the first barrier 120 can beformed of a flexible material, such as natural rubber or syntheticmaterial of similar flexibility, e.g., a flexible plastic, or be formedof a rigid material, e.g., a rigid plastic, e.g., polyetheretherketone(PEEK) or polyphenylene sulfide (PPS).

Assuming the wiper blade is a sheet of uniform width, the wiper blade ofthe first barrier 120 can be positioned at an angle of 15 to 90 degreesrelative to the polishing surface 36 (see angle B in FIG. 3). In someimplementations, the wiper blade of the first barrier 120 is slantedrelative to the polishing surface, e.g., at an angle less than 90degrees. In some implementations, the wiper blade of the first barrier120 is oriented vertically, i.e., at a right angle relative to thepolishing surface. The wiper blade of the first barrier 120 can beoriented such that the wiper blade slopes, from top to bottom, in thedirection of motion of the polishing pad (see arrow A in FIG. 3).

In some implementations, the first barrier 120 is suspended from a firstactuator 124 that can control the vertical position of the first barrier120 relative to the polishing surface 36 and/or the down force of thefirst barrier 120 against the polishing surface 36. Alternatively or inaddition, the first actuator 124 can move the first barrier 130laterally over the polishing pad 30, e.g., radially.

The polishing liquid distribution system 100 also includes a secondbarrier 130 to spread the fresh polishing liquid that has just beendelivered by the dispenser 110 in an even film across the polishingsurface 36. The second barrier 130 is positioned “after” the location onthe polishing pad 30 where the dispenser 110 delivers the polishingliquid 105. For example, as shown in FIG. 2, if the platen 24 rotatescounter-clockwise as shown by arrow A, then the second barrier 130 ispositioned counter-clockwise of the dispenser 110. The second barrier130 is positioned between the dispenser 110 and the carrier head 70.

In some implementations, the second barrier 130 is a body that contactsthe surface 36 of the polishing pad 30 and generally blocks thepolishing liquid from passing underneath, except for any polishingliquid that may be present in the grooves 38 and/or a thin film ofpolishing liquid 105. The body of the second barrier 130 can simply reston the polishing pad 30, or be positively pressed onto the polishing pad30, e.g., by an actuator. In some implementations, the second barrier130 is a body that sits slightly above the surface 36 of the polishingpad 30, while still contacting the polishing liquid. For example, whenthe platen rotates, the body of the second barrier 130 could hydroplaneon the polishing liquid. In either case, the second barrier 130 can helpspread the fresh polishing liquid 105 a more uniformly across thepolishing pad 30.

In some implementations, the first barrier 120 is pressed into thepolishing pad 30 at a greater pressure than the second barrier 130. Insome implementations, the first barrier 120 contacts the polishing pad30 whereas the second barrier 130 sits slightly above the surface 36 ofthe polishing pad 30 while still contacting the polishing liquid.

The second barrier 130 can be generally elongated body, e.g., a linearbody, and can be oriented substantially perpendicular to the directionof motion of the platen 24, e.g., generally along a radius of the platen24. Alternatively, the first barrier can be canted at an angle relativeto the radius of the platen, e.g., 10-30°.

The second barrier 130 can be parallel to the first barrier 120.Alternatively, the second barrier 130 can canted at a greater anglerelative to the radius of the platen than the first barrier 120.

In some implementations, the second barrier 130 is a curved body, e.g.,as shown in FIG. 2B. The second barrier 130 can curve such that the endcloser to the outer edge of the platen 24 is further along the directionof motion (shown by arrow A) than the end that is closer to the centerof the platen. The second barrier 130 can curve such that the concaveside faces in the direction of motion.

The second barrier 130 can be equidistant along its length from thefirst barrier 120. Alternatively, the radius of curvature of the secondbarrier 130 can less than the radius of curvature of the first barrier120. This can result in the distance between the first barrier 120 andthe second barrier 130 increasing along the radial direction toward theedge of the platen 24.

A leading surface of the second barrier 130 be oriented at an angle of15 to 90 relative to the polishing surface 36. In some implementations,the leading surface of the second barrier is slanted relative to thepolishing surface, e.g., at an angle less than 90 degrees. In someimplementations, the leading surface of the second barrier is orientedvertically, i.e., at a right angle relative to the polishing surface.The leading surface of the second barrier 130 can slope, from top tobottom, in the direction of motion of the polishing pad (see arrow A inFIG. 3).

In some implementations, the second barrier 130 is a wiper blade. Thefront surface of the wiper blade provides the leading surface of thesecond barrier 130. The wiper blade of the second barrier 130 can beformed of a flexible material, such as natural rubber or syntheticmaterial of similar flexibility, e.g., a flexible plastic, or be formedof a rigid material, e.g., a rigid plastic, e.g., polyetheretherketone(PEEK) or polyphenylene sulfide (PPS). In some implementations, thewiper blades of the first barrier 120 and the second barrier 130 areformed of the same material.

Assuming the wiper blade is a sheet of uniform width, the wiper blade ofthe second barrier 130 can be positioned to form an angle of 15 to 90degrees between the leading face 132 of the wiper blade and thepolishing surface 36 (see FIG. 3). Having the wiper blade of the secondbarrier 130 positioned at an angle can help push fresh slurry into thegrooves, thus reducing the presence of used slurry that reaches thesubstrate.

In some implementations, the wiper blade of the second barrier 130 isslanted relative to the polishing surface, e.g., at an angle less than90 degrees. In some implementations, the wiper blade of the secondbarrier 130 is oriented vertically, i.e., at a right angle relative tothe polishing surface. The wiper blade of the second barrier 130 can beoriented such that the wiper blade slopes, from top to bottom, in thedirection of motion of the polishing pad.

In some implementations, the wiper blades of the first barrier 120 andthe second barrier 130 form the same angle with the polishing surface36. In some implementations, the wiper blade of the first barrier 120 isoriented vertically whereas the wiper blade of the second barrier 130slopes, from top to bottom, in the direction of motion of the polishingpad.

In some implementations, the second barrier 130 is suspended from asecond actuator 134 that can control the vertical position of the secondbarrier 130 relative to the polishing surface 36 and/or the down forceof the second barrier 130 against the polishing surface 36.Alternatively or in addition, the second actuator 134 can move thesecond barrier 130 laterally over the polishing pad 30, e.g., radially.

Each actuator 124, 134 can be a pneumatic actuator. For example,referring to FIG. 5, each actuator can include a lower body 150 to whichthe barrier, e.g., the wiper blade, is secured, an upper body 152 thatis held by a support, e.g., an arm, and a bladder 154 trapped betweenthe lower body 150 and the upper body 152. Inflation of the bladder 154thus controls the vertical position of lower body 150 and the barrier120, 130 and/or pressure of the barrier 120, 130 on the polishing pad.The bottom of the bladder can be secured, e.g., adhesively secured, tothe lower body 150, and the top of the bladder can be secured, e.g., byclamping rims of the bladder, to the upper body 152. Either actuatorscan be another kind of actuator, e.g., a linear motor or piezoelectricactuator.

In some implementations, the first barrier 120 and the second barrier130 are suspended from the same actuator.

Referring to FIGS. 4 and 5, each barrier 120, 130 can be suspended froman arm 160. For example, the upper body 152 of each actuator 124, 134can be mounted on a plate 164 that is secured to the arm 160. The arm160 can be connected to an actuator 162 that is configured to move thearm 160 laterally across the platen 24. For example, the actuator 162can be a rotary actuator to sweep the arm 160 in an arc (see arrow C).Although FIGS. 4 and 5 show a common arm for both barriers, there couldbe separate arms with separate actuators.

Referring to FIG. 6, rather than a separate thin wiper blade, one orboth barriers 120, 130 can be provided by body having a flat lowersurface 170 that extends parallel to the polishing surface and that ispressed onto the polishing pad or slightly spaced from polishing padwhile still contacting the polishing liquid (e.g., hydroplaning). Thisbody can be formed of a relatively rigid material, e.g., a ceramic, or ahard plastic such polyetheretherketone (PEEK) or polyphenylene sulfide(PPS). For example, as shown in FIG. 6, one or both barriers 120, 130can be provided by the lower body 150 of the corresponding actuator 124,134.

For either barrier 120, 130, the body that forms the barrier can have aleading surface 172 (on the side that the polishing pad first passesunder). In some implementations, the leading surface is a verticalsurface. In some implementations, the leading surface 172 will push thepolishing liquid.

For either barrier 120, 130, the barrier can also include a splash guard174 to inhibit splashing of polishing liquid that impinges the leadingsurface 172. The splash guard 174 can be vertically spaced from thelower surface 170 and extend horizontally from leading surface of thebody in a direction opposite the direction of motion of the polishingpad rotation.

Alternatively, for either barrier 120, 130, the barrier can include aspreader 176. The spreader 176 projects from the leading surface 172 ofthe body and has a bottom surface that is sloped relative to thepolishing surface. An angle D between the bottom surface of the spreader176 and the polishing surface can be 15 to 75 degrees. Similar to thesloped wiper blade, the sloped bottom surface of the spreader 176 canhelp push fresh slurry into the grooves, thus reducing the presence ofused slurry that reaches the substrate.

In some implementations, the first barrier 120 includes a splash guardand the second barrier 130 includes a spreader 176.

Returning to FIGS. 2A and 2B, the second barrier 130 can be spaced fromthe first barrier 120. In some implementations, the wiper blade of thesecond barrier 130 is oriented parallel to the wiper blade of the firstbarrier 120. The first barrier 120 and second barrier 130 can be thesame length (along their longitudinal axis), or the second barrier 130can be shorter than the first barrier 120. The first barrier 120 canextend entirely to the edge of the platen 24 and/or polishing pad 30,whereas the second barrier 130 can be spaced apart from the edge of theplaten 24 and/or polishing pad 30.

Referring to FIG. 3, in some implementations, the dispenser 110 ispositioned such that the polishing liquid 105 is delivered onto atrailing face 126 of the wiper blade of the first barrier 120. Due tothe angle of the wiper blade relative to the polishing surface 36, thepolishing liquid flows down the trailing face 126 and then onto thepolishing pad 30 in the area between first barrier 120 and secondbarrier 130. An advantage of delivering the polishing liquid 105 ontothe wiper blade is that the polishing liquid tends to flow laterallyalong the wiper blade, and thus the polishing liquid is delivered alonga wider area to the polishing pad 30. Consequently, the polishing liquidcan be spread more evenly across the polishing pad 30, and polishinguniformity can be improved. However, as shown in FIG. 1, in someimplementations the polishing liquid 105 is dispensed directly onto thepolishing pad 30 (this would be applicable to either a vertical orslanted wiper blade).

Referring to FIG. 3, in operation, the leading edge 122 of the firstbarrier 120 will block the used polishing liquid 105 b. Most of the usedpolishing liquid 105 b will be deflected and run off the edge of thepolishing pad 30, although some of the used polishing liquid 105 b inany grooves 38 in the polishing surface 38 will pass below the barrier120.

On the other hand, fresh polishing liquid 105 a will be delivered by thedispenser 110 to the area between the first barrier 120 and the secondbarrier 130. The fresh polishing liquid will similarly be blocked by theleading edge 132 of the second barrier 130. Depending on the flow rateand spacing between the components, fresh polishing liquid 105 a mightpool in the area between the first barrier 120 and the second barrier130. However, some of the fresh polishing liquid can flow into thegrooves 38, displacing the used polishing liquid 105 b. As a result,significantly less used polishing liquid can reach the substrate 10, andthe defects can be reduced.

Although the first barrier 120 and second barrier 130 are illustrated asseparate components, they could be two walls of a connected singlehousing. There may be an open chamber in the middle of the housingbetween the two walls which can contain the polishing liquid.

As shown in FIG. 3, in some implementations, one or both barriers 120,130, e.g., the wiper blades, can include a first portion 140 at an acuteangle relative to the polishing surface 36, and a second portion 142that is parallel to the polishing surface 36. A rounded portion 144 canconnect the first portion 140 to the second portion 142. The barrier canbe pre-formed in this configuration, or the barrier may be a flexiblematerial that is initially planar but deforms into this configurationwhen pressed downwardly against the polishing surface 36. Thisconfiguration can help to push the fresh polishing liquid 105 a into thegrooves 38 to improve exchange with used polishing liquid 105 b.

By blocking used slurry, the amount of polishing by-product reaching thesubstrate can be reduced, and thus defectivity can be reduced. Inaddition, without being limited to any particular theory, by increasingthe amount of fresh slurry in the grooves, the concentration ofinhibitor and active agent (for metal polishing) passing into contactwith the substrate can be increased. This can make the polishing processless sensitive to pattern density, and dishing and erosion can bereduced. Conversely, again without being limited to any particulartheory, by blocking used slurry, the concentration of copper ions can bedecreased, which conserves the inhibitor for reaction with the metalsurface.

Controlled positioning (shape, device dimension, pad coverage, mountingposition on the pad, etc.) of the first barrier 120 and/or the secondbarrier 130 can be used to direct fluid off the platen 24 or towards thesubstrate 10 depending on the desired flow paths.

Controlled downforce on the first barrier 120 and the second barrier 130can be used to adjust the ratio of fresh polishing liquid versus usedpolishing liquid flowing below the second barrier. In someimplementations, the second barrier 130 is pressed against the polishingpad 30 at a lower pressure than the first barrier 120. In someimplementations, the second barrier 130 is spaced higher above thepolishing pad 30 than the first barrier 120.

By controlling the dispensing location or dispensing pattern of thepolishing liquid using the slurry distribution system 100, the polishingprofile can be adjusted and polishing uniformity can be improved.

Although the discussion above focuses on physical barriers to thepolishing liquid, it would also be possible to use jets of air to blockthe polishing liquid. For example, an arm could extend over thepolishing pad, and pressurized gas, e.g., air or nitrogen, could bedirected through a slot or plurality of holes in the bottom of the armtoward the polishing pad. With proper selection of the gas flow rate,the gas could block the polishing liquid. In addition, it would also bepossible to use a vacuum to suction used polishing liquid off thepolishing pad; such a vacuum could be applied through a slot orplurality of holes in the bottom of the arm that extends laterally overthe polishing pad.

A controller 90, e.g., a general purpose programmable digital computer,can control the flow rate of polishing liquid 105 from the reservoir,and control the actuators 124, 134 in order to control the down forceand/or position of the barriers 120, 130 on the polishing pad 30.Measurements from an in-situ monitoring system can be fed to thecontroller 90, which can adjust polishing liquid flow rate and/or thedown force of the barriers and/or position of the barriers to compensatefor polishing non-uniformity.

The controller 90 can also be connected to the pressure mechanisms thatcontrol the pressure applied by carrier head 70, to carrier headrotation motor 76 to control the carrier head rotation rate, to theplaten rotation motor 21 to control the platen rotation rate, or topolishing liquid distribution system 100 to control the slurrycomposition supplied to the polishing pad.

The polishing liquid distribution system can be used in a variety ofpolishing systems. The polishing pad can be a circular (or some othershape) pad secured to the platen, a tape extending between supply andtake-up rollers, or a continuous belt. The polishing pad can be affixedon a platen, incrementally advanced over a platen between polishingoperations, or driven continuously over the platen during polishing. Thepad can be secured to the platen during polishing, or there can be afluid bearing between the platen and polishing pad during polishing. Thepolishing pad can be a standard (e.g., polyurethane with or withoutfillers) rough pad, a soft pad, or a fixed-abrasive pad.

A number of embodiments of the invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the invention. Forexample

-   -   The leading barrier (the first barrier) could be used without        the trailing barrier (the second barrier).    -   The trailing barrier (the second barrier) could be used in the        polishing system without the leading barrier (the first        barrier).    -   The dispenser could be supported on or an integral portion of        the first barrier and/or the second barrier. For example, the        dispenser could be a flexible tube supported on the first        barrier.

Accordingly, other embodiments are within the scope of the followingclaims.

What is claimed is:
 1. An apparatus for chemical mechanical polishing,comprising: a rotatable platen having a surface to support a polishingpad; a carrier head to hold a substrate in contact with the polishingpad; a polishing liquid distribution system, the polishing liquiddistribution system including a dispenser positioned to deliver apolishing liquid to a portion of a polishing surface of the polishingpad, and a first barrier spaced apart from the dispenser and positionedover the polishing surface before the portion of the polishing surfacewhere the dispenser is to deliver the polishing liquid and configured toblock used polishing liquid being carried on the polishing surface fromreaching the portion of the polishing surface, wherein the first barrierincludes a solid body having a portion with a leading surface to contactthe used polishing liquid, wherein the portion of the first barrier thatcontacts the used polishing liquid curves about an axis perpendicular tothe polishing surface.
 2. The apparatus of claim 1, wherein the platenis configured to rotate to provide a direction of motion below the firstbarrier, and the first leading surface of the first barrier is curvedsuch that such that a concave side of the first leading surface of thefirst barrier faces in the direction of motion.
 3. The apparatus ofclaim 1, comprising a second barrier spaced apart from the dispenser andpositioned over the polishing surface after the portion of the polishingsurface where the dispenser is to deliver the polishing liquid andconfigured to spread fresh polishing liquid on the polishing surfacedelivered by the dispenser to the portion of the polishing surface,wherein a second leading surface of the second barrier curves about anaxis perpendicular to the polishing surface.
 4. The apparatus of claim3, wherein the platen is configured to rotate to provide a direction ofmotion below the first barrier and the second barrier, the first leadingsurface of the first barrier is curved such that such that a concaveside of the first leading surface of the first barrier faces in thedirection of motion, and the second leading surface of the secondbarrier is curved such that such that a concave side of the secondleading surface of the second barrier faces in the direction of motion.5. The apparatus of claim 3, wherein a radius of curvature of the secondleading surface is less than a radius of curvature of the first leadingsurface.
 6. The apparatus of claim 3, comprising a first actuatorconfigured to adjust a height of the first barrier relative to thepolishing surface and/or a pressure of the first barrier on thepolishing surface, and/or a second actuator configured to independentlyadjust a height of the second barrier relative to the polishing surfaceand/or a pressure of the second barrier on the polishing surface.
 7. Theapparatus of claim 1, comprising a first actuator configured to adjust aheight of the first barrier relative to and/or a pressure of the firstbarrier on the polishing surface.
 8. The apparatus of claim 1, whereinthe solid body has a flat bottom surface.